One or more aspects relate, in general, to processing within a computing environment, and in particular, to facilitating such processing.
Computers of a computing environment include central processing units (CPUs) or processors that control processing within the computers. Behavior of a central processing unit is controlled by control registers. Control registers are processor registers that perform particular tasks, such as interrupt control, switching the addressing mode, paging control and/or coprocessor control, as examples.
Control registers are typically implemented as latches, such as solid state elements directly on a processor chip. Some computers use a large number of control registers, as defined by the architectural implementation of the computers. Thus, control registers represent a growing area of the chip.
Moreover, some computers support multi-threading in which a central processing unit can execute multiple processes or threads concurrently. Each thread uses a separate set of control registers; thereby, increasing the number of control registers on a chip.
An increasing number of latch-based control registers may affect performance, chip area and/or power consumption. For instance, control registers are switched during context switches, and thus, an increase in the number of control registers, increases the cost of context switching. Further, with latch-based control registers, updates to controls occur in program order, which may also affect performance.
Different architectures may have different names for control registers. For instance, in the Power Architecture offered by International Business Machines Corporation, Armonk, N.Y., the control registers are referred to as special purpose register (SPRs). Other architectures may use other names. The use of control registers herein includes control registers of other names, including, for instance, SPRs, as well as others.